Optical transmission systems, including optical fiber communication systems, have become an attractive alternative for carrying voice and data at high speeds. While the performance of optical communication systems continues to improve, there is increasing pressure on each segment of the optical communication industry to reduce costs associated with building and maintaining an optical network.
Quite often, optical communication systems require various types of optical filter elements. For example, diffractive filter elements may be used to effect the separation (demultiplexing) of individual wavelength channels in a wavelength division multiplexed (WDM) optical system. In addition, these refractive filter elements may be used to compensate for the ill-effects of dispersion, to include chromatic dispersion (CD) and polarization mode dispersion (PMD).
One type of diffractive optical filter is a Bragg grating. Bragg gratings are interferometric optical devices which have been employed in a variety of applications including multiplexing/demultiplexing applications and dispersion compensation applications. Bragg gratings may be used to reflect light of a wavelength which satisfies the Bragg phase matching condition, and which transmits all other wavelengths.
One useful technique for forming a Bragg grating is to selectively alter the index of refraction in a substrate in a periodic manner. This selective alteration of the index of refraction can be used to fabricate both Bragg gratings in which the period of the index of refraction is regular, as well as chirped gratings in which the period of the index of refraction varies as a function of distance.
What is needed is a batch meltable glass material which is photosensitive, and which overcomes certain drawbacks of conventional glass materials.